The present invention relates to mechanical connections for stackable modules, and more particularly to a stackable, recessed, locking, insulated thumbscrew that allows modules in a stack to be readily removed without affecting underlying modules in the stack.
In a modular product often a plurality of modules are stacked upon each other, with a base module in the stack being mounted on a main frame or platform. The connecting devices used for connecting a lower module to the stack are able to accept connecting devices for the next higher module in the stack. Generally some sort of tool is required to secure the connecting devices into place. In order to have the connecting device be flush with the surface of the module it connects there is a countersunk hole into which the connecting device is recessed when secured. However when a module is removed from the stack, the process of unsecuring the connector devices for the module being removed results in the loosening or unsecuring of the connector devices for the modules lower in the stack. These connecting devices are usually some form of screw mechanism, with a screw driver or the like being the tool required for securing or unsecuring the connecting devices.
First of all it is preferable to be able to secure and unsecure the connecting devices without the use of any tools, as the required tool may become lost or otherwise not be available, especially when in the field. However without a tool it is generally difficult to secure the connecting device in such a way as not to have the connecting devices protruding above the surface of the module being connected, which makes the stack xe2x80x9cthicker.xe2x80x9d Further when removing an upper module from the stack the connecting devices from the lower modules in the stack need to be restrained somehow so that they don""t become unsecured.
Therefore what is desired is a stackable, recessed, locking, insulated thumbscrew that may be manually installed and that is locked in place even when the thumbscrew above it in a stack of modules is removed.
Accordingly the present invention provides a stackable, recessed, locking, insulated thumbscrew that has a knurled cap, preferably of an insulated material or coating, which is slidably attached to a main screw body having an externally threaded end and an internally threaded end of the same pitch on a common axis so as to move freely along the common axis. A cap spring mounted on the main screw body urges the knurled cap upwards. The main screw body has bayonet pins that engage xe2x80x9cJxe2x80x9d shaped bayonet slots in the knurled cap for slidable movement between the two. The knurled cap also has locking surfaces that engage a locking feature in a module higher in the stack so that the thumbscrew is restrained when a thumbscrew for a higher module in the stack is loosened to remove such module. The knurled cap may be easily turned with respect to the screw body by applying finger pressure to the top of the cap and rotating so that the knurled cap xe2x80x9cpops upxe2x80x9d to be gripped easily for manual tightening or loosening. A coin slot in the knurled cap is provided in the event that mechanical assistance is needed to initially loosen the thumbscrew.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.